<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>Title</title>
  <style>
    html, body {
      height: 100%;
    }
  </style>
</head>
<body>
<iframe id="iframe" src="https://www.youbaobao.xyz" style="width: 100%; height: 100%"></iframe>
<script>
  const iframe = document.getElementById('iframe')
  console.log({iframe}, iframe.contentWindow, iframe.contentDocument)
  const app = iframe.contentDocument.getElementById('app')
  console.log(app)
</script>
</body>
</html>
